Each year cardiopulmonary bypass permits over 500,000 patients worldwide with disabling heart disease to undergo therapeutic cardiac operations. The essential goals of cardiopulmonary bypass for heart surgery are to provide life-support functions, a motionless, decompressed heart, and a dry, bloodless field of view for the surgeon.
In a basic heart-lung life-support system oxygen-poor blood is diverted from the venous circulation of the patient and is transported to the heart-lung machine where reoxygenation occurs, carbon dioxide is discarded and heat regulation (warming or cooling) is accomplished. This processed blood is then returned (perfused) into the patient's arterial circulation for distribution throughout the entire body to nourish and maintain viability of the vital organs. Although current venous diversion and arterial perfusion methods can be combined with other measures to effectively isolate the heart for cardiac surgery, they are associated with disadvantages and limitations which contribute significantly to patient morbidity, mortality, and health care costs. It is thus desirable to develop improved cardiopulmonary bypass devices and methods that are safer, less traumatic, and more cost effective.
In the prior art, the method of collecting oxygen-depleted venous return blood from a patient for transportation to the cardiopulmonary bypass pump (heart-lung machine) for re-oxygenation and temperature regulation consisted of three different techniques: (1) a single venous catheter was inserted directly into the right atrium; (2) two catheters were directed via right atrial insertion selectively into the superior vena cava and inferior vena cava; (3) the third technique required the venous catheters to be inserted through peripheral vein access sites with the distal tip of the catheter(s) thereafter positioned either in the right atrium and/or superior vena cava/inferior vena cava areas.
In the techniques where catheters were inserted via the right atrium, the surgeon had available three options of catheter types. Firstly, a simple type where all of the orifices or openings for passage of blood into the catheter were positioned within the atrial chamber; or secondly, a two-stage type wherein some openings were positioned in the atrial chamber and others were located at the tip of the catheter device and positioned in the inferior vena cava; or thirdly, where two individual catheters were inserted at separate sites into the right atrial chamber or caval (inferior vena cava/superior vena cava) structures and selectively directed so that all orifices or openings for passage of blood were positioned within the superior vena cava or the inferior vena cava respectively. Direct insertion of catheters into the right atrium or vena cava results in direct surgical trauma due to the holes which must be cut in these structures for catheter entry. A circular, purse-string suture, an atrial vascular clamp for controlling bleeding and closing the hole, adds to the operative time and the cost of the procedure. Surgical wounds in the atrium, inferior vena cava, or superior vena cava have the potential for causing complications including, but not limited to, hemorrhagic bleeding, cardiac rhythm disturbances, air embolism (introduction of air into the cardiac chambers), and extensive surgical adhesions. Furthermore, this approach requires a major invasive breast-bone splitting (sternotomy) or rib spreading (thoracotomy) surgical procedure to reach the atrium and make the insertion.
Cardiopulmonary bypass support can be either partial where only a portion of the blood returning via the superior vena cava (upper body) and inferior vena cava (lower body) into the right atrium is diverted into the pump (heart-lung machine); or, total, wherein all, blood returning via the superior vena cava and inferior vena cava is diverted away from the right atrium into the pump. There are clinical situations where it is advantageous to divert all venous return blood away from the heart. Total cardiopulmonary bypass contributes to cardiac decompression and decreases the detrimental effects of myocardial distention. Furthermore, it provides the surgeon with superior operating visibility of structures within the cardiac chambers which can be obscured if a substantial volume of blood is allowed to enter the heart. There are two methods in the prior art for achieving total cardiopulmonary bypass. The first required placement of tourniquet loops around the superior vena cava and inferior vena cava catheters. The loops are snugly tightened around the catheters in order to prevent blood from entering the atrium. In the second method, occlusion balloons mounted on selective superior vena cava and inferior vena cava catheters were inflated to prevent blood from reaching the right atrium. Both of these methods for total cardiopulmonary bypass capability require major surgical thoracotomy or sternotomy for access to the right atrium and caval structures. Direct surgical dissection of the inferior vena cava, superior vena cava, and right atrium for catheter insertion and tourniquet loop positioning not only adds to the operative time but also increases the risks of injury to these structures which could lead to bleeding, cardiac rhythm disturbances and scarring.
Although peripherally inserted venous drainage catheters of the prior art avoid direct cardiac trauma and can be placed without a major invasive chest incision (sternotomy or thoracotomy), they are not capable of establishing the condition of total cardiopulmonary bypass.
The technique of the present invention is to insert the venous catheters through a peripheral vein access site and thereafter position the drainage orifices in the superior vena cava and inferior vena cava areas. The catheter(s) features inflatable occlusion balloons that allow the choice of either partial (balloons deflated) or total (balloons inflated) cardiopulmonary bypass support. The insertion site(s) may be individual or a combination of choices of the femoral veins, iliac veins, subclavian veins, axillary veins, and internal jugular veins. The use of this technique has the advantage of avoiding a major chest incision as well as surgical trauma to the right atrium, superior vena cava and inferior vena cava. This eliminates costly surgical instruments, sutures, tourniquets, and operative time associated with the conventional approaches.
In the prior art, the method of delivery of oxygen-rich (arterial-ized) temperature-regulated blood from the cardiopulmonary bypass pump to the arterial circulation of the patient consisted of two different techniques: 1.) a simple, single lumen catheter (cannula) was inserted directly into the aorta (most often the ascending aorta). To make such an insertion, however, access to the aortic wall could only be achieved through a major invasive chest incision such as thoracotomy or sternotomy. Direct surgical trauma to the aorta occurs as a result of the hole which must be cut in the aorta for catheter entry. This hole is surgically repaired after removal of the catheter at the end of the operation but leaves potential for major post-operative bleeding. Other catastrophic complications related to direct insertion of catheters into the aorta include: (a) the risk of splitting the three layers of the aortic wall apart (known as aortic dissection) and (b), the risk of disruption of cholesterol and/or calcium deposits from the innermost layer of the aortic wall at the site of entry which can then be carried into the blood stream to occlude flow in distal arterial branches and reduce function in vital organs such as the brain (stroke), kidneys (renal failure), legs (gangrene), bowels (gangrene), liver (hepatic failure). 2.) The alternative prior art method for delivery of arterialized blood to the patient's circulation employed a simple, single lumen catheter which was inserted into a peripheral artery, either percutaneously or by using a surgical cut-down procedure. This technique avoided a major chest incision. While the two arterial methods of the prior art complete the loop of the heart-lung machine for basic life-support by returning blood to the patient, neither has the intrinsic capability of providing all optimal conditions (requirements) for heart surgery which will be discussed below.
In order to perform complex, delicate surgical procedures on the heart, i.e., coronary artery bypass and valve operations, it is desirable to establish a resting, non-beating (flaccid) non-distended state. This condition, along with a dry, bloodless field, is ideal for safe manipulation and suturing of cardiac structures, and furthermore, contributes to decreased metabolic cardiac energy demands while promoting preservation of cellular functions. In the prior art this non-beating state was accomplished by delivery of a cardioplegia (heart paralyzing) solution to the coronary circulation to stop the heart by one or a combination of two general methods: (1) Antegrade (cardioplegia infusion is initiated at the arterial end of the coronary circulation via the origins of the coronary arteries, i.e., ostia, in the aortic root and flows towards the capillaries within the heart muscle; (2) retrograde (cardioplegia infusion is directed into the venous circulation via a coronary sinus and flows backwards into the capillary circulation of the heart muscle). It is at the capillary level where the cardioplegia solution interacts with the cardiac muscle cells, resulting in its desired effects.
All prior art antegrade cardioplegic techniques for heart surgery required an occlusive vascular clamp to be applied to the ascending aorta to prevent arterialized blood from the cardiopulmonary bypass pump from reaching the coronary arteries, proximal ascending aorta, and aortic valve areas while at the same time maintaining arterial perfusion to all points distal (downstream) to the clamp. This isolation maneuver then allowed infusion of cardioplegia solution either directly into the coronary openings (ostia) via catheters, (cannulas) whose tips were inserted into the ostia or indirectly via a catheter (cannula) inserted into the isolated segment of the ascending aorta adjacent to the coronary ostia. Surgical trauma to the aorta resulted from the aortic puncture wounds or major aortic incisions that had to be made to use these techniques, both of which were dependent on major sternotomy or thoracotomy for exposure. The use of the surgical clamp to squeeze the opposing aortic walls together also has major disadvantages. For instance, a major invasive surgical incision (sternotomy or thoracotomy) is required to reach the aorta in order to apply the clamp. By the compressing or squeezing action of the clamp, fragments of cholesterol or calcium in the aortic wall may break away and embolize to the vital organs downstream. In cases of very severe calcification of the ascending aorta, it is not feasible to apply an external clamp because the compressibility of the aorta has been lost. Surgeons must then resort to less optimal, more complex methods of bypass support, myocardial protection and heart isolation which further increases the likelihood of post-operative complications. There are situations where the surgeon cannot proceed with the operation and it is terminated (abandoned) with the patient losing the opportunity for definitive therapeutic treatment of his disabling heart disease. Retrograde prior art cardioplegia delivery methods also are dependent upon major invasive chest operations as well as direct trauma to the atrium for their use. Again, the patient is being subjected to increased risks of bleeding and direct cardiac trauma. The present invention eliminates the need to distort the aorta with a clamp by integrating an occlusion balloon into the arterial perfusion catheter which when positioned in the ascending aorta and inflated appropriately will provide the same function without the risks. Antegrade cardioplegia delivery in the present invention conveys blood into the isolated segment of the ascending aorta just below the aortic occlusion balloon into the coronary ostia, avoiding the need for aortic puncture wounds, aortic incisions, purse-strings or surgical repair.
Prior art methods of controlling distention (decompression or venting) and improving visibility of the heart during heart surgery included: (1) insertion of a catheter via the left atrium or a pulmonary vein which was then directed across the mitral valve so that its openings at the tip were positioned within the left ventricular chamber for suction evacuation (also called venting) of blood; (2) inserting a catheter directly into the apex of the left ventricular muscle so that its openings at the tip were positioned within the left ventricular chamber for suction evacuation (venting) of blood; and (3) the prior art catheter placed in the isolated segment of the ascending aorta for antegrade cardioplegia delivery could alternatively be switched to a suction source to accomplish aortic root venting (decompression) but not left ventricular decompression (venting). All of these methods have the disadvantages of requiring major sternotomy or thoracotomy and are associated with direct cardiac and aortic trauma. The present invention provides for both aortic root and left ventricular decompression integrated into the arterial perfusion catheter which can be inserted remotely without a major chest incision, cardiac trauma or aortic trauma.
When surgeons are required to perform repeat open heart surgery (known as "redo" operations) in someone whose chest has previously been entered via a major sternotomy or thoracotomy, extensive adhesions are usually encountered which obliterate the natural relationship and appearance of anatomic structures. This distortion further increases the risks of injury and massive fatal hemorrhage during the process of exposing, isolating and preparing structures for catheter insertions (arterial, venous, cardioplegia, left ventricular vent) and therapeutic repair. The present invention allows peripheral insertion, institution, and maintenance of cardiopulmonary bypass to take over the circulation prior to opening the chest or at any time thereafter when major hemorrhage, cardiac instability, or other complications arise which lead to deterioration of the patient's condition.
Major invasive chest incisions are often associated with a higher incidence of morbidity including, but not limited to, intraoperative and post-operative bleeding, resulting in the likelihood of increased blood transfusion requirements, returns to surgery for re-exploration to control hemorrhage, longer healing and recovery times, pulmonary complications (such as lung collapse and pneumonia), catastrophic wound infection (mediastinitis), extensive scarring and adhesions, mechanical wound instability and disruption (dehiscence), chronic incisional pain, peripheral nerve and musculoskeletal dysfunction syndromes. Developing a system with features that avoid surgical maneuvers, instrumentation and devices known to be associated with increased morbidity and mortality is desirable. Such improvements have the likelihood of resulting in a favorable impact on patient care, quality of life, and health care costs. The present invention for cardiopulmonary bypass during heart surgery integrates multiple functions which were not available in the prior art and has the advantage of avoiding a major chest operation and its potential complications.